As an optical scanning device for use in an image forming apparatus such as a color printer, there is one type of optical scanning device which includes: an optical deflector including a polygonal mirror and for deflecting light from a light source; an imaging lens for forming an image of the light deflected by the polygonal mirror, on each of a plurality of photosensitive drum; a temperature sensor, and a housing. The housing has spaces each receiving therein a respective one of the imaging lens and the optical deflector, separately. The temperature sensor is installed in the space receiving therein the imaging lens, in adjacent relation to a radiator plate for the polygonal mirror.
In this optical scanning device, an internal temperature of the housing is detected by the temperature sensor installed in the space separated from the space receiving the optical deflector therein. Based on a temperature detected by the temperature sensor, positional deviation in scanning applied to the photosensitive drums by the polygonal mirror due to deformation of the housing caused by heat generated from a drive motor for rotating the polygonal mirror is calculated, and a timing of the scanning by the polygonal mirror is corrected according to the calculated amount. The above conventional technique is intended to correct the timing of the scanning by the polygonal mirror, based on a temperature detected by the temperature sensor, to thereby suppress the occurrence of mis-color registration in a color image corresponding to electrostatic latent images formed on the respective photosensitive drums through the scanning by the polygonal mirror.